Impact of Porosity Type on Microstructure and Mechanical Properties in Selectively Laser Melted IN718 Lattice Structures

Laser Powder Bed Fusion (LPBF), one of the most employed additive manufacturing techniques for metals, has opened new dimensions in realizing strong and weight reducing structures. In this study, Inconel 718 (IN718) unit cell designs, were fabricated through the LPBF technique and analyzed. Among the plethora of lattice structures in existence, BCC, BCC-Z, FCC, FCC-Z, Gyroid, Diamond and Schwarz structures have been selected to focus on. A relationship between the mechanical properties including yield strength, failure stress and strain, and hardness with each type of unit cell was established. Also, the effect of the possible defects on the hardness value was examined using microstructural analysis on samples. Scanning Electron Microscopy (SEM) analysis was also performed to examine the possible defects and its effect on the hardness of the as-built part. The SEM images of the grain structures indicated higher levels of isotropy in Gyroid, and Diamond samples compared to the rest of the samples which relates to the load bearing capacities of each unit cell structure. A similar trend was observed in terms of the uniformity of meltpool which can be linked with the consistency in yield characteristics. Further, Diamond and BCC-Z structures displayed high values of hardness in comparison with rest of the samples.